Do not even propagate future headers #525

nfrisby · 2023-11-28T00:55:37Z

@njd42 and I came up with this idea a couple weeks ago, during a chat about the vagaries of NTP/clocks/etc.

See the commit message of the 'consensus: do not even propagate future headers' commit.

The main concrete benefits:

It's a step towards Chronos and that helps simplify/ground our story around future blocks.
A network-load optimization of sorts: if someone with a horribly out of sync clock sends a block 60 seconds early, the direct neighbors won't even propagate it.

nfrisby · 2023-11-28T01:05:13Z

...s/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/InFutureCheck.hs

+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeApplications #-}
+
+module Ouroboros.Consensus.MiniProtocol.ChainSync.Client.InFutureCheck (


@njd42 Please confirm this logic matches what you and I chatted about a few weeks ago. Thanks!

@njd42 It's being merged now, but I'd still appreciate your thoughts on this module. Thanks.

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

nfrisby · 2023-11-28T01:14:48Z

FYI, the PR is draft because I've so far only propagated the ChainSync client interface change to its test. I'll tackle the rest tomorrow.

Edit: No longer Draft.

amesgen

Looks great, mostly minor comments and a few suggestions. Will review again after the chores (formatting, compilation failures, changelog entries, etc.).

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Fragment/InFuture.hs

...boros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs

amesgen · 2023-11-28T10:59:39Z

...boros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs

Note to other reviewers: The diff here is much smaller when using sth like difftastic.

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

...s/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/InFutureCheck.hs

...boros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

...sensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Network/NodeToNode.hs

...oros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/NodeKernel.hs

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

...boros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

nfrisby · 2023-11-29T19:03:26Z

Just FYI, I just now rebased onto origin/main---there were no conflicts.

nfrisby · 2023-11-29T20:55:44Z

CI is green 👍

amesgen

LGTM (after squashing), only very minor comments left

ouroboros-consensus/test/consensus-test/Test/Consensus/MiniProtocol/ChainSync/Client.hs

nfrisby · 2023-11-30T16:54:18Z

FYI: I based a second time to sign the commits.

Main change: remove the LogicalClock, since it's quite a bit of indirection with no real gain. Also, remove -XRecordWildCards.

This an aggressively-simple interpretation of the easy part of Ouroboros Chronos in the presence of The Header-Body Split. (The hard part is the _synchronization beacons_---which need to be propagated promptly, and will be implemented much later.) Other less-aggressive interpretations would propagate future headers/blocks but set them aside. But this seems much simpler and within an RTT or two, assuming eg the NTP clients are well-configured.

This now exercises the real ChainSync InFutureCheck.

njd42 · 2023-12-04T08:48:39Z

...s/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/InFutureCheck.hs

+            now <- systemTimeCurrent systemTime
+            let ageNow         = now `diffRelTime` onset
+                syntheticDelay = negate ageNow
+            threadDelay $ nominalDelay syntheticDelay   -- TODO leap seconds?


I think that we can resolve the leap second argument now. Worst case is a 0.9s jump (see https://en.wikipedia.org/wiki/DUT1). So the two extrema are:

local clock adjustment is +ve by 0.9s : the delay here would be (up to) 0.9s 'too much' - this is not an operational issue, delays of that magnitude occur during usual operation

local clock adjustment is -ve by 0.9s: this could be perceived by other nodes as a (minor) future arrival and therefore delayed there by a small amounr.

The handling of leap seconds is (and will likely forever be) a bit of mess (see https://en.wikipedia.org/wiki/Leap_second#Issues_created_by_insertion_(or_removal)_of_leap_seconds).

As we only ever take the slotToWallClock time direction we would be safe as this is always (to UTC) unambiguously defined. The mapping in the other direction is (around leap seconds) ambiguous depending on the operating system's handling of leap seconds.

njd42

It all looks good to me - I've added some comments as to why I believe that you have already effectively dealt with the leap second issue (as best as can be done)

nfrisby added the enhancement New feature or request label Nov 28, 2023

nfrisby requested review from amesgen and njd42 November 28, 2023 00:55

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Add far future blocks to the ChainSync client test #526

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amesgen mentioned this pull request Nov 29, 2023

ChainSync client test: decrease number of tests without any sent headers #529

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Block forge should check for pending future blocks in ChainDB #579

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nfrisby added 2 commits November 30, 2023 09:02

consensus-test: improve legibility in the ChainSync client test driver

53223fd

Main change: remove the LogicalClock, since it's quite a bit of indirection with no real gain. Also, remove -XRecordWildCards.

nfrisby added 2 commits November 30, 2023 09:02

consensus-test: include near-future headers in ChainSync client test

a39cd95

This now exercises the real ChainSync InFutureCheck.

Update changelogs for ChainSync.InFutureCheck

8bb0efc

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Merged via the queue into main with commit 3a1fde0 Nov 30, 2023
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Block forge should check for pending future blocks in ChainDB #579

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Do not even propagate future headers #525

Do not even propagate future headers #525

nfrisby commented Nov 28, 2023 •

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Do not even propagate future headers #525

Do not even propagate future headers #525

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